The present invention is directed to actuators for valves and dampers, such as used in controlled heating, ventilating and air conditioning (“HVAC”) applications. Depending upon the control system being used, such HVAC actuators typically act for a relatively short period of time (a few seconds up to a minutes or two), typically running a few times (perhaps five to ten movements) a day. In the most common applications, the HVAC actuators use a small electrically powered motor which runs at many rpms, through a gear reduction unit to increase torque and reduce the angular output of the HVAC actuator so it appropriately turns the attached valve stem or damper handle.
Some HVAC actuators operate in noisy environments (such as in an industrial plant) or in locations that are not sensitive to noise. Other HVAC actuators, however, are placed in office environments, in libraries, in residences or in other locations that are much more sensitive to sound and noise issues. When the HVAC actuator works to open or close the valve or damper, it can generate sound/noise which disturbs occupants of the building. Such sound/noise can be particularly disconcerting in that the person hearing the HVAC actuator often does not know what device created the sound/noise, or why the sound/noise occurred at that particular moment in time. Accordingly, HVAC actuators should work as quietly as possible. In general, the sound generated by a working HVAC actuator has been viewed as a necessary evil, with the only viable options being to either add a more expensive motor in the HVAC actuator design (leading to a more expensive product), or to have the installer sound insulate around the HVAC actuator or around the motor within the HVAC actuator. Both options increase the total expense of the HVAC actuator. Better solutions are needed.